Telephone-exchange system.



E. E. CLEMENT.

I TELEPHONE EXCHANGE SYSTEM. APPLIOATIONQFILBD APR. 6, 1907. 1,109, 19, V Patented Sept. 1; 1914 5 SHEBTSSHEET 1.

E. E. CLEMENT. TELEPHONE EXCHANGE SYSTEM.

/ APPLICATION FILED APR. 6, 1907. 1,109,619, Patented Sept. 1,1914

5 SHEETPBHEHT 2.

B. B. CLEMENT;

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED APR. 6, 1907.

Patented Sept. 1, 1914.

5 8HBETSSHEET 3.

Elvwzntoz Wit no E. E. CLEMENT.

TELEPHONE EXCHANGE SYSTEM. APPLICATION FILED APB.6,1907

1.,1O9,619 Patented Sept. 1, 1914.

5 SHEETS-SHEET 4.

is vwantb'c E. E. CLEMENT.

TELEPHONE] EXCHANGE SYSTEM.) APPLICATION FILED APR 6, 1907.

Patented Sept. 1, 1914.

5 SHEETS-SHEET 5.

UNITED STATES PATENT OFFICE.

E. CLEMENT, OF WASHINGTON, DISTRICT OF COLUMBIA, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 FREDERICK O. STEVENS. 0F ATTICA, NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

To all whom it may concern.

Be it known that I. Rows-no E. CLEMENT, a citizen of the United States, residing at, Washington, in the District of Columbia, have invented certain new and useful Improvements in Telephone-Exchange Systerns, of which the following is a specification, reference being bad therein to the accompanying drawing.

My invention relates to telephone en'- c hange systems, and particularly to $81111: automatic systems in which automatic switches or their equivalent are employed to effect interconnection of lines as determined by manual apparatus controlled through the agency of operators.

My invention has for its object the provision of a number of sets of switching ap- Speci'flcation of Letters Patent.

Application filed April 6, 1907.

aratus sufficient for the probable needs of i the service, but not necessarily equal to the number of lines, and most desirably less than the number of lines; the provision of operatorscontrolling sets less in number than the number of lines, and the distribution of the load, that to say, the incoming calls, among the sets of switching apparatus, and among the operators, whereby uniform efiiciency in service may be attained.

For the sake of simplicity in description I shall specify herein automatic switches of the type known as Strowger selectors and connectors. the construction of such switches being well shown in Letters Patent No. 815,176 and No. 815,321, granted to Keith and Erickson, March 13, 1906. The circuits commonly employed with these switches are well known -to those skilled in the art. 1' shall also specify'a type of common battery i line circuits and central office talking circuits which are considered standard, and generally known as two-wire bridged battery circuits. It is to be under stood however that in specifying the apparatus and circuits nienticned they are used as types for purposes of descriptlon. and not as limiting the invention.

btated in terms of the embodiment thus presented, the present invention comprises a number of groups of selector and connector switcnes less than the number of lines to be served; a number of primary selector switches normally set back to a fixed or zero position. and adapted to connect the calling lines with thesald-igroupsof selector and Patented Sept. 1 1914.

Serial Nor 366,849.

connector switches; a number of operators selective keys and impulse transmitting means controlled thereby, with automatic secondary selector switches normally set scribers, and may actuate the appropriate selectolfl and connector switches to connect the calling and the wanted lines. By having all the primary and secondary selector switches normally set back to zero, I eifect a uniform distribution commencing always with the first trunk or the first position. \Vhen a subscriber calls in, current in his line energizes a relay which starts up his primary selector switch, said switch continuing to progress step by step until its wipers restupon the terminals of an idle trunk, at which time the cut oil' relay of the line receiyes current from the switch circuit, the switch stops, and the secondary selector switch is started to connect the trunk to an idle ()Ptl'fltOYS circuit. An appropriate signaling means such as a lamp, is provided for each operator-s circuit, and the operator befng thus apprised of a call is able to connect her telephone through her circuit to the trunk and thence to the calling line, and afterward to transmit impulses to the trunk and forward to its automatic first selector switch to secure connection with the line wanted. Testing and ringing of the wanted line are automatic.

' The specific distinguishing feature of the invention claimed in the present case is that each line has a terminal selector switch by by which it may be connected in calling to an idle trunk line leading to a first selector switch; and each trunk line is provided with a switch starting up from a zero or normally inoperative position to select and connect.

ing. however, and have cleared out the connection, this trunk selector or secmidary lector switch again becomes available.

My invention is illustrated in the accompanying drawings in which-- Figure 1 is a diagram showing a calling snbscribens line and a portion of the central ottice equipment. Fig. 2 is a similar diagram coinplenn-ntary to Fig. 1. and intended to he placed below the latter. showing another portion of the central oilice circuits. 1 Fig. 3 is a similar diagram also comple i mentary to Fit. 1. intended to be the right of the latter. and showing a selector and connector switch with their circuits. through which the calling line may be connected with any one of a considerable number of other lines. Fig. -l is a diagram of 'circuits complementary to lie. intended to be placed at the right of the latter. Fig. :3 is an end view of an improved placed at rotary selector switch. Fig. 6 is a tut'ftlOIl on l the line X-X of Fig. 5. Fig. 7 is a similar view with the bank contacts removed. of a modification ot the switch shown in Fig. Fig. 8 a view of an improved vertical selector switch and Fig. 9 is a modification of the switch shown in Fig. 8.

Retina-in; to Fig. l. A is a snbscribers station connected to the cen. ral oilice by line wires 1 and L. whiih are n rmally connected through the contacts of a cut-oli' relay X to the line relay M and the gr und. respectively. the line relay being c nnected to the main battery B through the wire 3. Line extensions 4, and 5 pass from the cut-off relay to the wipers of a step by step selector switch S, this switch being what is called a "single motion or rotary switch. having! a spindle s journaled so that it can turn upon its axis. and provided with a ratchet \\llttl by which it may be turned. This ratchet wheel is engaged by a stop or detent pawl z' contiollcd by the ele tromagnct a. and a stepping or working pawl controlled by the cl ctroinmlnct The cir uit of the electro magma .v" is controllcd by the line relay .\l

through it armature m. for which purpo ithe front contact T ol the relay is connected y a wire 8 with the magnct a. while the a 'riaturc n1 is connected through an interrupter 1 with the battery wire 3. This interruptcr i roniinnonsly operating and may t onsist. as hown. cl :1 rotative cylinder ha v ing alt rnate 'oil ltlctillti' and insulating! portions. one conduct r being connected with f the conducting portion and another with a pen bearin upon the "ylindcr. o that as the cylinder rotates the onnluctors will be alternately c nne ted together and dis onnected a the pen successively bears upon the con ducting and insulating portions. The cylinder is continuously driven y any suitable means. \l'ith such an arrangement it isonly necessary to maintain the circuit closed.

its armature. it also turns the spindle s by means of its pawl and the ratchet on the spindle, any retrograde inoiion of the spindl being prevented by the fixed stop pawl controlled by the ma a'nct a. The spindle is provided with a rctnrn spring. preferably a coiled spring. which has a constant tendency to turn the spindle l)2l(l\' against the pawl 01' the magnet s. and which when this pawl released by the enerniwation of it magnet. will actually turn back the spindle into its normal. Zero or inoperative position. The mechanical construction suitable for a switch 5 as described will be set forth hereinal'ter. The line relay M also partially controls the circuit of the release magnet .s'. For this purpose the armature m is connected to the main battery wire 3 through the branch 43. The circuit of this release magnet is normally open at the springs a and 1/, which are worked a device on the spindle a, bein open when the spindle is llilth in zero position and closed so soon as it leaves that position. The release circuit is further controlled by the cut-oil relay N, through a bacl; contact 11 connected to the wire 12. and cooperating with the armature 2.". whi h is grounded through the wire 12. in order that the relay magnet a may be energized. therefore. it is necessary for the switch to be set away from its normal position. and for the relays i\l and N both to be deincrgized. This condition is only brought about when a connection has been made and the subs ri ers une hung up their receivcrs. The switch S has in its banlv's trunk conta ts a. which cooperate with the switch wipers a. and the test or signaling contacts s which coi'iptuate with the wipers 8' The multiples of these bank contacts which are shown in Fig. 1 are of course supposed to be distributed in ditl'er nt switches. the wires from each tr"nl being multiplied to asmany line switches as may be desired. convcnient arrangement contemplates l ltl mnl' tiplcs. thcre being ten trunks. and ach trunk bcin; rcprcscnnal by a multiple con tact in each line switch ol Loo lincs. l lacl: line thus has a cess to ten trunks. and ea h line switch need only have ten sets ol' conta ts s. a in it banlv lnstcad ol' using a rotary witch. I may make the single innti n i the switch vertical. the contacts a. a then bcin; arranged in vertical rows and thc wipers .v". a being stepped up along the rows by means of the nnm'nets a". When the release magnet s works the spindle a will then be restored by gravity: and the springs o and I) will be placed beneath the spindle so that its weight will open them. The contacts .9, s are the terminals of trunk circuits, and one of these trunk circuits is shown in Figs. 1 and 3, leading to a selector switch S. This trunk is marked 13, 14. 15, 16, and its extensions 5 in Fig. 2-5 are marked 17, 18. A pair of coin densers G is interposed in the circuit. for

the purpose of separating the same into two portions for battery currents, these currents being fed both in the operation of the system. Across the answering end of the trunk, 13-44, are bridged the two relays R and R, with the main battery B between them. The tip relay R is grounded, and the sleeve relay R is connected to the live side of 15 battery, which is the usual arrangement in circuits of this type. The tip relay R responds to the act of the calling subscriber and controls the clearing out of the automatic apparatus; the sleeve relay becomes energized when the switch S picks out an idle trunk, and then closes the circuits of the magnets R R", R", which are respec tively the stepping magnet of the secondary or operating selector switch S, a cut-cit relay for the operators circuit wires 19, 20; and a locking relay serving also as a cutofi' relay for shifting the control after the operators circuit is connected. The functions of these several relays will best appear from the statement of their operation hereafter. The relays R and R are combined cut-ofi' and repeating relays. The relay B when energized over the operators wire'QO pulls up its armature, breaks apart the wires 36 15 and 17, and connects the latter to the Wire 21 leading to the battery wire 3, so as to send an impulse of current through the trunk wire 17. Similarly, when the relay R is energized over the operators wire 19. it

pulls up its armature to break apart the wires 16 and 18, and connects the latter to the wire 22 and thence to the battery wire 3, thus sending an impulse of current forward over the trunk wire 18. When both of these relays R and R are simultaneously energizcd, they connect the operators wires 19 and 20 to the wires 15, 16, respectively, so that the operator may connect her telephone to said wires 15 and 16 and communicate with the calling subscriber. I l The multiple test contacts 8 are connected by a wire 23 to the point .r, and thence through two branches to the battery wire 3. One of these branches, 24 contains a resistance 27 and the other or shunt branch, 25,

, contains practically no resistance. .This latter branch, 25, is normally closed through a buck contact of the armature i" of the relay R". whereby the contacts a are connected 0 directly to the battery B, so the test condition of an idle trunk is that these contacts have their potential raised to the full voltshunt branch 25is broken, whereby the re sistance 27 is interposed between the battery and the contacts 8. This condition continues while the circuits are in use, and suffices to give a busy test. since the cutoff relay N of each line is connected through a wire to the wiper 8 of the line switch S. This wiper passes over the contacts 8 when the switch is operating and the cut-off relays are so wound and adjusted that they will pull up on direct battery connection, but will not pull up on the connection through a resistance 27. Their arrangement is such, however. that any relay which has already been pulled up will hold up on onehalf the current flow through the resistance 27, so that when the wiper 8 of a line switch over the terminals 86 of trunks which are already busy, the relay N of the calling or testing line will not pull up, but the relays of the lines already in use will continue to hold up.

The trunk wires 17 and 18 extend as shown in Fig. 3 to the side-switch arms 8 and s of the selector switch'S This switch is of the Strowger type referred to in the beginning of my specification, having a main spindle arranged for both vertical and rotary movements, this spindle being placed at the axis of a set of contacts arranged in ten rows of ten each. Carried on the spindle are talking-circuit wipers 8 which cooperate with the bank contacts s and a test u ipcr s which cooperates with the multiple test contacts a. The switch spindle is stepped up to bring its wipers opposite the desired row of contacts by means of the socalled vertical magnet 0) controlled through a. relay V; and the rotary movement ofthe switch is brought about by means of a vibrator magnet '0' which makes and breaks its own circuit as it vibrates and is controlledby the relay T when the side-switch arm 5 is in its second or intermediate position. It is unnecessary to give here any extended description of the circuits and apparatus of Fig. 3, all of these being old and well known to those skilled in the art.

Q is a release relay of the switch and 1 is the release magnet governed thereby.

The other parts of the apparatus as well as the circuit COIlIlections will sufiiciently appear from the statement of operation hereinaftcr.

S designates a connector switch which is designed to cooperate with a selector switch S it has a similar spindle carrying wipers s and 8 The test is made on the tip or upper side of the line. This switch also contains line contacts in its banks arranged in rows of ten each. The spindle is stepped up to bring the Wipers s "oppos1te the desired age of the main battery. When the relay R 1 row by means of a so-called vertical magnet becomes energized,hcwever, which of course v, and is rotated step by step by means of a 66 occurs when the trunk becomes busy, the lso-called mt-ary'magnet vflsvhich in this .:asc. is not a vibrator but responds to distinctire cu rrnt unpuises, since the desired line is identified with a single pair of contacts only, and therefore the row of contacts must be selected and the pair of contacts in the row at'tcrw'ai d picked out by the wipers, before testing. in this resides the principal ditl'ercnce bet ween the connector and selector switch, the purpose of the selector switch being to pick out and connect with an idle trunk line in any desired group. In the operation of the selector switch, therefore, the spindle is stepped up by means of definite and distinctive. impulses to the row of contacts and s represtnting the desired group (which may be either thousands or hundreds and in this case is hundreds), and after that, when the side switch has taken one step, the rotary magnet t" takes control ol the switch and steps the spindle around continuously as lbng as thewiper 8 finds ground on the contacts a. \Vhen this ground fails (the busy contacts being grounded and the idle ones open) it means that an idle contact has been reached, and thereupon the side switch is moved a third step to cut off the rotary magnet and stop the wipers upon this ungrounded or idle contact.

The connector circuit contains a pair of condensers (V for the reason that the forward impulses which work the switch must not be confused by the battery current supplied to the called subscriber. We may assume that the switches of Fig. 3 are both in the same building with the apparatus of Figs. 1 and 2 although thi is not at all necessary, and in such cases the battery B shown separate in the two ligures is of course the same battery. For the purpose of supplying talking current to the called subscriber, I connect this battery to the sleeve conductor 44 of the connector switch. through a relay R and I ground the tip conductor 43 through the relay R which is the same as connecting it back to the battery. Thus, the main battery is also bridged across the conductors 43 and 14 through the relays Ii and R which as in the case of the re ays h and It in Fig. l are wound each, but present currents.

It is the ringing relay, which controls the application of the ringing generator G to the called line and is itself controlled on the one hand by the relay it and on the. other by the commutator K. which may be comhigh iinpedencc to voice mon to all the ringing relays ot' the exchange. The circuit of the ringing relay is indicated at 4.7-, 4c, 47. 48, 49 and 50, being terminated at the ground through the commutator on one end and at. the battery Wire 3 on the other end. This circuit is controlled by the relay Ii and this relay does not become energized until the side-switch to ap u'oximately 100 ohms 7 arms 8 s, 8 and 8 have made their laststep so that the conductors 43 and 44 are completed from the condensers C to the i Wipers s and .9 Before this last step of the side-switch is taken, the wipers s and have been placed upon the terminals of the wanted line, and the release relay Q, has been applied to the tip side of the line for the purpose of testin The circuit of this i relay is as follows: 51. 52, 53, 54, 55, a, 56 to tip wiper a. If the line wanted is busy, there is a ground on the tip side. either by way of a relay It or by Way of a relay R depending on whether the line originated the call upon which it is engaged, or was called by some other party. In either case the test or release relay Q. will receive current; but if there is no ground because the line wanted is idle, then the test relay remains unaficcted, the talking circuit is completed, and the sleeve relay R becomes energized by current passing to the wiper s and thence through I the multiplecontact 8 (see Fig. 1) and the cut-elf relay N to ground. The cut-off relay thereupon pulls up and the ringing relay circuit is at the same time completcd, so that the commutator K takes control thereof. It will be observed that this circuit 46-47, etc., passes through a back contacton the relay R", which is controlled on one side by a pair of contacts under the foot of the pindle of the switch S and on the other side by front contacts of the tip relay R which does i not pull up until the called subscriber l answers. When this occurs, the relay R l becomes energized, locks itself by way of J wires 50 and 51'. and opens the ringing relay circuit 41', 47., 48, etc. The relay R is i controlled by the subscriber in the intervals l of ringing, for it will be observed that the l l l l l commutator K has segments whereby it closes the ringing circuit: at intervals only. \Vhile this circuit is open, therefore, and the relay R" deenergized in consetplence, the 511i)- 1 scriber has control of the relay R In order vthat the relay R may remain energized through the ringing intervals. I provide a special battery connection. as shown. l The arrangement of switches shown in i Fig. 3 is sutiicicnt tor exchanges up to 1000 iline capacity; but in order to provide for l more than 1000 lines, another set of selector switches is required. interposed between the i trunk ends of Fig. l and the switch S of Fig. 3. The capacity of the exchange can he. incr ased indefinitely without altering these circuits by adding these sets or groups of switches in the well understood manner. The selector switches ill have the same cirlcuit as that shown at S and therefore I l have considered it unnecessary to multiply illustration by showing more than one. It i is within the power and skill of every pew ison having a fair knowledge of the automatic art to add as many sets of schctors as may be desired. Regardless of the num-' ber of switches, the method of operation, which has an important bearing upon the operators equipment, is to send the selectmg or working impulses over the trunk wire 17, which is commonly called the vertical wire, and to send the controlling impul es over the trunk wine 1-8 which is commonly alled the rotary wire. These soal d rotary impulses serve to work the side-switch magnets T and T, and thereby to shift the side switches so as to bring into play successively the vertical and rotary magnets, the test relay, etc. 1.5 Referring now to the lower part of Fig. i 1 and Fig. 2, I have therein shown an operators equipment and the trunk selector witch for connecting a calling trunk therewith. The trunk switch is marked S and is similar in its oonstmctionto the primary selector or line switch 5. It has a spindlfi a and wipers s, a, and s. It is rotated by means of a pawl and ratchet actuated by a vibrator magnet R and is held in the position to which it is turned by a stop pawl controlled by the release magnet 8 The circuit of the rotary vibrator mognet is closed through an interrupter 1 similar to I by the sleeve relay B of the trunk and openedby the relay B, which it will be recalled is controlled by the relay R, which rooeiues current when an idle operators set has "been reached. The release maiguetw" has its circuit controlled by the re ay R, which in turn is controlled initially through the oneratcrs wire 20 and the switch wiper n and after that wiper has stopped on the operators the relays B and R jointly, these being the starting and stopping relays of the operators outfit. In order to enable this description to be followed readily, i may state again that the switch S starts 11 from zero as soon us the sleeve relay of the trunk has pulled up, that is to say as soon as the trunk l3-- 14 comes into connection with a calling line. The wipers s", a, and a then sweep over the contacts 8, s and s of the respective operators wires, until they reach the contacts of an idle operators setfwhen the switch /S is stopped. After the operator has performed her functions and the connection throu h H trunk wines 1718 is completed to t e wanted subscribers line, the release: magnot a restores the switch S to its zero or inoperative fossition where it remain during the coninuance of the connection.

In the lower part of Fig. 2 I have shown the apparatus which appears in front of one o orator, consisting of'a set of buttons only. Above these in the figure I have shown a, set of Wheels or sections of a drum with the cooperating springs, the'motor, and the commen commutator of the central ofl'lee sending trunks 18, 14:, 15

contact, by"

ing machine. This machine furnishes the impulses by which the selector and conmotor switches are Wlllkfld in order to select the line wanted, and the number of impulses sent as well as their arrangement is determined by means of the operators keys or buttons. T hose keys are in three sets, K, K and. K, each not having ten buttons controlling cmitsct springs k, 10 The springs In of all the buttons in each set are oined to a. common wire, and the ends of those three common wires are connected together at the point In, from which point the conductor leads as shown in Figs. 2 and 1 to the multiple contacts a in the banks of the various mink switches S of the answerand 16. The spring 11 of each key is connected to a pen on the approprinte disk or zone on the sending machine drum. \Vhen any particular lmtton is depressed, therefore, it connects its individual wire to the common wire 70. The individual wines of the keys K are marked respectively 71, 72, 7s, 74., 15, 7c, 77, 7s, 79, 80. Similarly the individual wires from keys K are marked 81, 82, 8B, 84, 85, 86, 87, 88, 89, 90, and the individual wines of the keys K are marked 91, 92, 9B, 941 96, 96, 97, 98, 99, 100. The sending me ino comprises the main commutator I), having a brush d connected to the main battery, and riding over its segments so as to produce regular recurring makes and breaks in a continuous series. In practice this commutator is made with a pair of spring con-' tacts and teeth or cams are formed on the body of the commutator to work these springs up and down, but for convenience of illustration I have isown the brush reabing directly on the periphery of the disk. With such a construction in actual practice and considering that this commutator will carry a large number of switching impulses simultaneously. I prefer to make the brush d of carbon. This is a detail, however, which may be varied at will and does not affect the invention. The commutator D is gra hicclly shown us carried on a shaft d which extends through all of the number wheels forming both the mechanical 1 electrical connection therewith. The ma chagiicei connection is not shown in tho drawing but the electrical connection is indiccted by a wire marked a3. The number wheels are shown at d, d, d, d, at", cl, (1', d, d, d, each having a tooth or raised segment of a suitable length to cover the space of the number of teeth on the commutator D equal to the number of impulses the particular wheel is to transmit. Thus the first wheel 01' has a single tooth d, approub mately equal in length to only one tooth on the main commutator. The second wheel has a single tooth d approxlmatily equal in length to two tooth on the cqmumtawr,

theoo and so on. In other words. a set of number wheels each and breaks through a number of teeth, I have all the makes and breaks on the main c mmutator, and in order to send any desired number of impulses, l seleet a wheel which will maintain eonneetion with the rumniutator while the desired number of impuses are being produced and is then cut il therefrom. Another peculiarity of the ar rangenient is that the makes and breaks on the number wheels ll, (1*, 2!, etc., are made during the passage of gaps on the main commutator when there is Zero p tential and hence there. will be no sparking. at the number wheel contacts. In order to do this I may either subdivide the eonnnutator sur face evenly and equally into alternate cor.- durting and insulating segments and th n make each number wheel tooth slightly longer than the partieular tooth to whirh it. corres 'mnds. or I may make the i-ondurting p rtions on the eoniniutat r small r than the insulating portions ant make th number wheel teeth of lengths e aril to the exart multiple of a unit subdi ision. it will be. observed that there are tour sets of s on the number whelsTHhese will art-our modate four sets of keys K. K etr. ll a greater number of digits appear in the numbers to be transmitted. the wheels must be provided with additional sets of springs. The set K has its individual wires 'on net'ted to the first set of springs ll. the set K has its individual wires eonuerted to th set of springs d. and the keys l\'" are siun larly connected to the spring pens 1/. The i .leneral dirertion of rotation l the lt llk mutator and the various wheels connected t it is eloi-kw'ise as shown by the arrows in Fig. 2. and the teeth on the wheels rome into rontart with the spring pens in the order (5. ll. 4/ Thus the number set up n the set'of buttons l\' is transmitted over the wire first. then follows the num er set up on the buttons h. and so on. Thus for the number ills the op rator would depress ol' whieh makes the 'l'ourth button in the set l\'. the sixth button in the set l\" and the eighth button in the set h? lly traeing' the rireuits it w ll he l'ound that when the rontrollin; rirruits are t'loHtl. whirh orrurs at the beginning ot' a rotation when the wheels are all in the position shown in Fig. "J. current will pass from the main attery to the r mniutat r l). thenre to the wheel 1/". thenre y wire T1 to the f urth key in the set K and theme to the wire To and so on to the wire 20 and the. relay ll in Fig. l. w'hirh repeats the im- ])l|l.*-t t\(l' titiuk wire 17 to the switrhes. .\s the wheels rontinue their r tati n. this i'it'l'uit will be broken after four impulses hare b en transmitted. and then a new eirruit will be formed earrying eurrent from I the battery through the commutator to the t instead of using the rela} lt" The i'oiitat'ts ol the ditl'erent sixth wheel at". and taenee from the seeond spring rib on that wheel through the wire Sh to the key whit-h is elosed. thenee to the wire To and them-e again to the relay R whieh repeats to the switehes. After these impulses ha ibeen sent by this route, this eiri-uit will be broken and a new eireuit will e formed from the main battery through the rommutator l) to the eigl'ith wheel to the third pen thereon. thenee t the eighth key in the set K". whirh has een el se'l. theme to wire I and to the relav it as efore. The rlosures between the whee s and sue 'essh e :ets ot slu'inqs a e arranged ltbe eparat d by ntervals. during w'hh'h no rurrent at. all llows. to the wire it); The e iuteri al are ueres ary in order to per mit the switehmj riir u to he rearrai'itred so as to i l' tltltt (he l l ll' results M pouse to the .\It(\" e sets ol w rking impulses. la other i'l. ha in;- shown herein a set i" Hirowger sw'it 'hrr .l must provide not only the re tiial or working iiiipu s in groups. at l mat al o pr vide the in t l'p sed tarji impulses between said grout. l his is Ilt'l llilflll. li1tl by means at the whirl whith his tour teeth et in llltlill'r ture. and all adapted t make eontart with the single pen if. whi -h is eonllt' trd y the wire til to the'niultiple irona -ts in the banks of the various trunk stiii'lor :\\'ilt'lll l S. and theme through the wi e l." t tho relay bf. whieh repeats the r tary impulses o er the trunk wire 18 to the switi-he v The wheel 1]" is insulated l'r m the bai't 1/". and is grounded through the wire h t. this being neres ary heeause is r nnerted on its other side to battery wire ii. In other words. the repeating relay ll whirh is eontrolled by the num bot wheel is a gro nded relay and s the numbe whet-ls itllfl' battery impulses from the w'mmulator to w rk it: out the relay R hour-e the r tary wheel 11" 1v n batt ry. use the giw-uud to work the relays. The reason I make one oi these relays ground d and the ether to battery is in rder to pull them th up simultaneously w hen. the operat r has her teleph n et r dged :ieross the \\i1(.* To and H in Fig.1.

l it serto the elrrtor :w it -lir i'rl'erred to 1 r S hyo {wen i l'eriial to onl as do elei-triii-i ruits and ront a ts with whi h th y are awiated and in this i'tltlil li lti ill. .lia n-:umnat r illuste-itious in l'it'j. hr e been ullii-ient. 'lhe meelianr ral t'wu'ires ot' sw'iti-h adapted to pertorin the t'uurtions ot' the sw'itt'hes rs :ml S of Fig. l are shown in ligs. 53 and 41. This switrh rouip ises a transe a on wiieh is mounted a bank ll l ioutarts eou i ting of ten rows of eontarts of three rontarts eaeh. rows are adapt ed to be sui-i-essi ely engaged by wipers (1 and 0 w hirh are fixed upon the r tatable shaft f, the three contacts 0, d and e being respectively insulated from each other. A spring 9 interposed between the shaft f and a stationary part as the frame, tends to rotate the shaft 7 to one limit of movement, when the contact-arms carried by the shaft will not rest upon any of the bank contacts as shown in Fig. 5. Fixed upon the shaft f is a ratchet h. The teeth of this ratchet are so constructed that a pawl enga 'ng therewith will preirnt movement 0 the shaft under the influence of the spring 9'. Adapted to engag with the ratchet h are a holding pawl i and a stepping pawl is. The pawl i is pivoted upon the frame and its nose is normally held in engagement with the ratchet by means of a spring I. The pawl Ii: is pivoted to the armature m of the step ping magnet .9 which armature is in turn pivoted to the frame of the magnet or upon any other suitable stationary portion. The armature m is normally held retracted by a spring 0 while the nose of the pawl .l" is thrown outwardly by means of a spring 7! extending between the armature m and the tail of the pawl Ir. The outward movement of the nose of the pawl is is limited and it is guided in its movement by a stationary pin in order that the holding pawl i may be disengaged from the ratchet It so that the contacts upon the shaft f may be re -rned to their normal position under the innuence of the spring 9', a magnet a, known as the release magnet is proiided. The armature s of the release magnet is retracted by means of a spring i. this -.1r;na ture being limited in its outward movement by a nut u in screw-threaded engagement with a screw 1' mounted upon the frame of the magnct and extending through the armature 8 Obviously the nut u is capable oi adjustment along the screw 7' to permit grcatcr or less movement of the armature s. Carried by the armature a of the re lease magnet is a resilient arm 11 which carries a ratchct tooth .1" adapted to engage with the lower end of the holding pawl 1'. An arm 3/ mounted upon the armature m of the tepping magnet overlaps one end of the arm i and is adapted to draw down one cnd of that arm so that the lower end of the pawl 1' will clear the tooth. :1! when the armature of the stepping magnet is at tractcd. The operation of the apparatus is as follows: Assuming the parts to be in position as shown, as impulses are supplied to the stepping magnet its armature will be attracted a number of times equal to the number of the impulses and at each attraction the pawl k will be thrown forward into engagement with the ratchet wheel and will move that wheel forward a distance de pending upon the adjustment of the various parts, which are so adjusted that at the first impulse the wipers upon the shaft ,f

just described will be moved into engagement 'w i'li the first row of bank oofltadvs and will be movdd to a succeeding row upon each impulse thereafter. The shaft and wiperwwhioh it carries will be prevented from retrograde movement by the holding pawl which is forced into engagement with the ratchet h by its spring. A desired row of the bank contacts having been reached in the manner described and the object for which the connection was established having been accomplished, it becomes necessary to return the wipers to their zero or normal position in readiness for another operation'as just described. This restoration is effected by do energizing the release magnet 8', it having been previously energized, when its armature will be retracted. drawing the tailof the holding pawl 2'. with it, and the nose of that pawl will be disengaged from the ratchet h and the wiping contacts will be returned to their initial position. In the next selective operation of the switch, however, it is necessary that the. holding pawl i shall engage with the ratchet h to hold the contacts in any position to which they may be stopped. to release the pawl 27 from the arm prior to the succeeding stepping operation. This is accomplished by means of the arm g which upon the first energization of the stepping ma et and the attraction of its armature, wil draw down with it the free end of the resilient arm 10 thereby freeing the pawl 11 whereupon its nose will. be thrown against the ratchet h by the spring Z. Carried upon one of the wipers c, d and 6 upon the shaft 7', is a projection a of insulating material adaptel. when the removable contacts are intheir normal position, to bear against one of, and close the contacts a and b which are so mlounted as to be insulated from each other but which are normally in engagement. These contacts correspond to those referred to by the same reference letters in Fi .1.

I t will be noted in regard to the switch that the release of the wipers occurs upon the det nergization of the release magnet. the holding pawl being position to engage the, ratchet and restrain the wipers so long as the release magnet remains energized after having once been excited. It may be, however, that it will be of service for the release of the wiper contacts to occur upon energization of the release magnet and for the holding pawl to in disengaged from the ratchet even thoughthe release magnet may he dei nergized. A structure adapted for operation in this manner but in other respects like the switch just described is shown in Fig. 7. On reference to this figure it will be seen that the holding pawl a is pivoted at c and its nose is normally held in engagement with the It. therefore, becomes necessary ratchet by the spring d. The tail of this holding pawl is adapted to be engaged by armature a of the release magnet s. Vhen this release magnet is energized, its armai spring 1 and so:- is l and its contacts in ture i attracted and the holding pawl a" nun ed against the spring a" so that it clears the ratchet. when the wiper contacts are free to return to their initial position. When the armature s is attracted, it carries with it the resilient arm n, the tooth :0 of which latches behind the stationary detent The holding pawl is thus locked away 'l'roi'n the ratchet until, at the first impulse in the stepping magnet .9 at the beginning of another selective operation, the arm y drawn downwardly and unlocks the arm at from the stationary detent, whereupon the holding pawl comes into engagement with the ratchet. The operation of this switch is in all respects similar to that of the switch in Figs. 5 and 6 except as to the releasing means above indicated.

The selector switches in Figs. 5, 6, and 7 are of the rotary type. It may be, however, under some circumstances, desirable to use vertical or rectilinearly moving switches. Such a switch is shown in Fig. 8. This switch comprises a vertically moving bar a having ratchet teeth 0 upon one side while upon the other side are mounted contacts 1;", (l and 6 each of which are adapted to engage respectively with the sets of contacts f and 72. each of the corn tacts c", and 6 being adapted to suecessively engage with the contacts oi" its 1'0 spective set as the bar a is moved vertically. To step up the bar a vertically a stepping magnet i is provided. The arma ture A of this magnet is pivoted at and normally retracted by the spring m To the end of the ari'nature Z' which is adjacent to the bar (i -"2 is pivoted a pawl 71.". The nose ot the pawl 21 is thrown toward the teeth If" upon the bar by means of a spring 0- secured at one end to the tail end of the pawl If and at the other end to the armature Z. The nose of the pawl n is guided in its movement by a stationary pin p l'pon each energization of the stepping up magnet its armature A? will be attracted and the pawl n will be thrown upward and against the ratchet teeth 2 the adjust ment being such that at each energization of the stepping magnet the bar a will be mo ed up a distance corresponding to a predetermined --tep which shall be such as to cause the col-darts 1"". and c to move from their initial position into connection with the first set of bank contacts and from each set to the succeeding set. It will now be apparent that the contacts upon 4"" wiil be i moved into conncction with any desired set 1 01' bank contacts by supplying the proper number of electric impulses to the stepping magnet. A holding pawl g mounted in end a po t such a manner as to be capable of moving into and out of engagement with the teeth 6", is normally held in such engagement by \es to retain the bar a. any position to which it may be stepped by thestepping magnet. then however, the object of the established connection has been accomplished it becomes necessary to return the switch to its initial position from which it may be again operated for selective purposes. To accomplish this result a release magnet s" and its appurtenant parts are provided. The armature t of this release magnet is normally retracted by a spring 11? and carries a resilient 'arm '03, one end of which adapted when moved toward the holding pawl to ride over a ratchet tooth to upon that pawl and to interlock with said tooth, whereby the holding; pawl is moved with the armature of the release magnet when that armature is moved in the other direction. It will now be apparent'that upon encrgization of the release magnet its armature will be at tracted while the end of the resilient arm w will ride over and snap back of the tooth 1c. When. the release magnet is dei ner 'ized the armature f together with the resilient arm and the holding pawl f will be retractedmy the spring 11- when the bar a and its colitacts will l e t ee, to return to th ir initial position under the action of gravitv. In order that the holding pawl may he in position t maintain the bar If by the tepping magnet during the next seleciia operation. it is necessary that the holding pawl shall be released from the re- .-training inlluencc oi" the spring 6 To this is prov ded whereby the aTinatures ol the ii' caw and stepping magn ts are placed in sue'h cooperative relation that upon the opcralilni oi" the armature of the stepping iriagnct. the holding pawl is dis engaged l'ioni the armature ol the release magnet. it will be apparent upon inspection of Fig. 8. that upon the encrgization of the stepping magnet and the attraction of its armature. that th post a will be thrust upward and will carry with it the end of the resilient arm r so that the holding pawl will be relea ed lliltl l'Ulll and will be thrown into engagement with the teeth upon the bar w?" by the spring The contacts y and ol' this ligure correspond to the ontact a. and ol' the rotary switch shown in Fig. 5. the contacts and .3 howewr, being separated by reason of the bar resting upon one oi them in its initial position.

in Fig. 9 is shown a switch in all respects similar to that shown in Fig. 8 except for ertain modifications of the release mechanism. It, therefore, becomes unnecessary to describe the apparatus shown in this figme other than to point out-wherein these modifications consist. In this last figure the armature t of the release magnet 8 is from the ratchet teeth upon the vertical bar, rides over a stationary projection z and is adapted to snap back of said projection so as to prevent the holding pawl from returning into engagement with the ratchet teeth of the vertical bar. Thebar will then drop to its initial position. Upon the energizing of the stepping magnet in the next selective operation, the post a will be thrust. upward thereby raising the tooth w and permitting the holding pawl to come into engagement with the ratchet teeth.

The operation of the system can be best set forth by tracing the connections and noting the operations of the various parts of the apparatus which are involved from the time a call is initiated at a subscribers station until the conversation has termi natedand the apparatus has been restored to its normal condition.

Let it, be assumed that a subscriber at a station as A desires to converse. He removes the receiver from its hook when the latter rises and establishes a connection, through his transmitter and receiver, between the lines 1 and 2. A circuit is then established from the free terminal of the battery B through the wire 3, line relay M. armature a, line 1, subscribers set, line 2 and armature n to ground. The relay M, being thus energized, attracts its armatures m and m, a circuit then being established from the free side of battery B through conductor 3, interrupter I, armature m, conductor 8 and stepping magnet 5' to ground. The

magnet is then intermittently energized,

as its circuit is made and broken by the interrupter, which results in the reciprocation of the stepping pawl Ir (see Fig. 7) and the stepping forward of the wipers of the switch S from one row of bank contacts to the next at each cnergization. In the initial position of the switch, the circuit of the magnet s is broken at the con tacts a, Z1 and the switch does not move from this position until the relay M is energized and then although the contacts a and b are closed, the armature m is attracted and the connection between that armature and wire 10 is broken. The release'magnet being thus dcenergizcd, the holding pawl 1' is in engagement with the ratchet wheel and holds the wipers in any position to which they may be stepped. The wipers are stepped from one row of bank contacts tothe next .in .the. ma nner described until the wipers 8 and 8 rest upon the contacts as s and s of an idle trunk, when the circuit of the cut off relay N is made from the ground throu h the relay, wire 28, wiper 8 contact s and Wire 23 to point as. From an the circuit passes through the branch 25, including the armature 1" of the relay R", to conductor 3, connected to the free side of the battery B. When a connecting trunk is in operation or busy the relays R R and R are energized when the circuit rom the point in through the branch 25 of neglible resistance will be opened through the circuit from the point referred to. A connection however, may be traced from the point 00 through the armaturcs of the relays R and R and the resistance 27 to the conductor 3. As has been before pointed out, this resistance is of such magnitude it will permit sufiicient current to flow, so that the relayN will hold its armatures after they have once been attracted, but the current will be insufficient to cause the relay -N to initially attract its armature. It will now appear as the wipers s and 8 pass over the contacts of busy connected trunks, that the arinatures of the relay N will not be attracted and the stepping of the switch S will continue until the test wiper 8" comes against the test contact 8 of an idle connect-.

ing trunk when a circuit of low resistance will be formed through the relay N of the calling subscribers line and the low rcsislance branch 25 of the idle connecting trunk whereupon the armaturcs of the relay N will be attracted. The arn'iatures n and n, of the relay N being thus removed from their back contacts,'the circuit of the line relay M will be broken and its armatures m and m will fall back whereby the armature m will come into contact with the back contact 9, while the circuit through the wire 8 of the stepping magnet s will be broken by the armature m and the stopping of the switch S will cease. The contacting of the armature m and the back contact 9 forms a connection whereby the circuit of the release magnet s is completed from the wire 3 through conductor 6, armature m, conductor 10, magnet s and contacts a, b (the.

switch S being out of its initial or zero position) to conductor 12. Inasmuch, however, as the armature n is attracted by the relay N. the circuit of the release magnet is broken between the armature referred to and its contact 11. The holding pawl of the switch, therefore, is in engagement with the ratchet upon the switch shaft so that the wipers are maintained in the position to which they have been stepped. The switch S having been stepped into position. as described, circuit may be traced from the free side of the battery B through the relay It to sleeve side 14 of the trunk thence through pm of the.multiple contacts s, one of tin wipers 8 the extension 1 of the subscribers line, armature n of the relay N, conductor 2 of the subscribers line, the subscribers instrument, conductor 1 of the subscribers line, armature n of the relay N, extension of subscribers line, the other wiper s of the switch S, the other multiple contact st, the tip side 13 of the trunk and the relay R to ground. A circuit having thus beencom pleted, the armatures of the relays R and R are attracted thus closing the branch circuit through the resistance 27 as before pointed out. In addition to the attraction, by the relays R and R of their armatures for completing the circuit through the resistance 27, these relays also attract their arinatures QT, 37" and 2r and 31". The attraction of the armatures 21" and 3r operates to close the circuits of the stepping relay R1 and the test wiper s, of the selector switch with ground. The circuit of the relay R may be traced from the free side of the battery B through the conductor 3, conductor 68, relay R interrupter I, conductor 62), armature r 'of the relay R", conductor 70, armature 2r and conductor 71 to ground. From the test wiper of the switch S, circuit may be traced through the conductor 101, relay R conductor I102, armature v", conductor 1.03 and armature 3r to ground. The armatures 2r and Sr are connected by a conductor 105 with the conductor 106,which when the relay R is energized and its armature r is attracted, is connected through that armature and a conductor 1.07 and conductor 3 with the free side of the battery. When the armaturcs QT and 37" are not attracted, the relay R being decnergized, these arrnaturcs will be respectively in connection with conductors 107 and 108 which are, re spcctivcly, connected to the tip and sleeve sides 15 and 10 of the trunk, connected so that when the relay R is deencrgized both sides 15 and 10 of the trunk will be connected with battery. The stepping relay R having its circuit closed, as described, the switch 5 will he stepped from one position to the next so that its wipers 8"", 8 and a will pass successively over the rows of banir contacts 8 s and 8. Upon the arrival of wiper s uponthe contact s circuit may be traced from the tree side of the battery B through conductor 109, armature r conductor 1.10, magnet It contact 111, contact 112, conductor 113, contact 8 wiper 8", conductor 20, armature r conductor 114 and relay R to ground. The relays R and R are thus connected in serics'and this results in the attraction of their armaturcs. The attraction of the armature 9' of the relay R however, results in the connection of that armature with the contact 111 and also in the separation of the contacts 111 and 112. This causes the ground connection of the relay R to be made through the armature 1", that armature being connected to ground as shown, while the cir cuit of the relay R is broken. The relay R is therefore, energized but momentarily. This momentary energization, however, causes the temporary contact of the armature r with the contact 115 of conductor 106, when circuit may be traced from the conductor 3 through the conductor 22, armature r contact 115, conductor 106, relay R, conductor 103 and armature 31 to ground The relay R is thus momentarily energized and attracting its armature 1" brings that armature against the contact 116 thereby transferring the battery connection of the relay R from that made through armature r to that made through armaturer' and conductor 107 to the conductor 3 and the free side of the battery. The relay R thus locks its own circuit so that it remains energized after the relay R has become de'e'nergized, The relay R being thus energized, its armature 1" will be attracted thus breaking the circuit of the stepping magnet R where upon the switch S will stop. The relay R attracts its armature 11" thereby breaking the circuit at this point of the relay R The relay R having been energized as described, its armatures 1r and 27' will )e attracted and circuit can be traced from the battery wire 108 through the armature 1r, conductor 120 and the lamp L to ground. The lamp will thus become lighted notifying the operator of a. call. Another circuit can be traced. from the battery Wire 109 through the armature 21' and corn ductor 121 to the contact 8 whence circuit will be traced through the wiper s, conductor 101, relay R and conductor 102 to a back contact of the armature 1'1" but at this point the circuit is opened, due to the energization of the relay R Circuit may also be traced. from the conductor 120 through conductor 123 and the release magnet 8 to ground. This magnet is thus energized and in this particular case the release mecha nism construction is shown in Fig. 5, having been described hcreinbetore. The holding pawl is therefore, in position to maintain the wiping contacts in the position to which they have been stopped; Connection may also be traced from the conductor 170 through the contacts 8', wiper a, conductor 19, armature 1r of the relay 1t and conductor 124, conductor 125 and relay R to battery wire 3. Connection may also be traced from the wire through contact is, wiper a conductor 20, arn'iature r of relay 1t", conductor 114 and relay R to ground.

Referring now to Fig. 2, it will be seen that the conductors 170 and 70 are adapted to be connected by means of the pressure of a button (1 with conductors 127 and 128, "which lead to an operators set of usual donstruction and hence not shown. It will be swar seen that upon the depression of the button 0, that a circuit will be completed from the battery wire at one side of the relay R" throu b that relay, the operators set, and the relay R to ground. Talking current will thus be supplied to the operators set and also the relays R and R will become energized, whereupon they will attract their respective armatures 11' and r and one of the operators conductors 124' will be connected with the trunk conductor while the other operators conductor 114 will be connected with the other trunk conductor 16. It will now be apparent that the operators set and the calling subscriber's instrument will be so connected that conversation may be had. The operators set and subscribefis instrument having been placed in conversational communication as described, the operator inquires of the subscriber the number of the wanted subscriber's station. Let it be as sumed that this number is 468. The operator depresses the fourth key of the set K. the sixth'key of the set K, eighth key of the In this manner the conductors 74, 86 and 98 are connected with the common point law, these conductors being respectively connected with the pen d of the drum section (P, the pen d of the drum section (1 and the pen a? of the drum section II. The commutator D is driven by a motor M and, the motor is supposed in the particular apparatus shown to be normally at rest, it becomes necessary to start the motor and commutator. To accomplish this, the operator depresses the button thereby connecting the conductor 130, which is connected to one terminal of battery to the conductor 13]. and thence through the conductor 32 to the relay R and to ground. The relay it" be ing thus energized, its armaturcs r and 11* are attracted when circuit will be closed from the battery wire 103? through the last mentioned armature, conductor 1:13 and re lay it to ground. The relay lt. being thus energized will attract its armaturcs r and 17'. The circuit ot' the relay ll to battery through the arnmture 1" is thus .broken but this connection is made through the armature r" of the relay It whcrcby the control of the relay R is transferred from the relay R to the relay K". (ircuit may be traced also from the motor conductor 131i through the armature 11''" and a motor starter as indicated which may be of any well known or suitable type, to the other motor conductor 135. The motor will thereupon start up and place the commutator in operation. There is also set in operation a starting disk (is, which is of conducting material with the exception of an insulating segment 136 upon which the pen 137 nor mally rests. After the motor and with it the commutator, starting disk, rotary disk and drum sections are set in operation by the depression of the key 0, as described the pen 137 will ride oil the insulating seg ment and maintain the circuit initially closed, by the depression of the button 0'. This circuit being closed, the motor, commutator and disks will continue to revolve until the pen 137 rests upon the insulating segment 136, when the circuit will be broken and the apparatus will stop,- During this rotation, first the pen 1" corresponding to the disk (l will be engaged by the contact segment upon the said disk, which is of such a length as to maintain the contact with the pen during four impulses of current through the commutator. The circuit over which these impulses are sent, may be traced from one terminal of the battery to the brush (l thence through the conunutator, thcconductor (P to the shaft of the drum thence through the drum to the segment of the disk d, the pen 15", the conductor 74, the contacts of the fourth button of the row K to the point has thence through the conductor to the contact 8" of the switch S, wiper s conductor 1'14 and relay R to ground. At each of the four impulses, the relay R will be energized and attract its armature 21' against its front contact connected with the battery B through the mnductors 21 and At each impulse, therefore, the tip side 17 of the trunk will be connected with battery and the impulses will be repeated over this side of the trunk to operate th auto matic selector and connector switches as be fore dcscribed; the next operation consists o'l.thc sending oi a rotary impulse l, occasioncd by the coming in contact with the pen a! of one of the onducting projections upon the disk (1. This action causes the closure of a circuit from the ground throughaconductor .lUi, disk pen (1, conductor 170. contact s of the switch 5%, wiper .s", conductor l9, armature iw, conductors 12 i, and 125 and the relay R to the batteiy wire 3. Each projection on the disk 1 is of such length as to transmit but one impulse and this im pulse passing through the relay R, in the circuit just traced, the relay last mentioned attracts its armature 1r against its front contact thereby connecting the sleeve side 18 of the trunk momentarily with the battery wire 3 through the conductor 22, when a rotary impulse transmitted over the sleeve side for working the side switches of the automatic selector and connector switches as before indicated. After the sending of the rotary impulse as described, the conducting segment of the disk d comes in contact with its pen (1, when six impulses are sent over the conductor 86 t0 the point 7cm, whence circuit is the same as before, through the relay it, and vertical impulses are transmitted over the tip side 17 of the trunk. The disk d 'tlren sends another rotary impulse over the sleeve side of the trunk as before and eight vertical impulses are then transmitted over the ti side by reason of the contact upon the disk d coming in contact with its pen all, connected with the conductor 98 through which connection is established to the point km, the circuit being otherwise the same as before, through the relay R and eight vertical impulses will be transmitted over the tip side 17 of the trunk; this is followed by the sending of a rotary impulse by the disk d" and then the apparatus is brought to a stop by reason of the pen 137 riding upon the insulating segment 136. At the close of the operation just described, the wanted subscribers line, unless it is busy, will have been connected as before described. The entry of the pen 137 upon the insulating segment 136 at the end of the connecting operation, breaks the circuit as before traced through the relay R which there upon releases its cuit of the relay R which is turn releases its armature thereby breaking the circuit of the release magnet 8 when (see Fig. 5) the holding pawl i will have its nose re moved from engagement with the ratchet upon the switch shaft and the switch will return to its zero position, thus leavin the operatofs set idle in readiness to per orm the connecting operation for a connecting trunk and a subscribers instrument.

The function of the relay R is to prevent interference with the connecting operation by reason of the passage of the wipers of the switch S over the contacts 8 s and s of busy operators sets. The relay R having been energized by the connection of the subscribers line to the trunk, circuit may be traced from the ground through the armature 3r, conductor 103, armature 1r, conductor 102, relay R conductor 101, contacts a and 7/ to the battery wire '108. The contacts a and b are normally opened, but are held closed when the wipers of the switch i" are in their initial position. In this initial position, therefore, the relay R is energized through the circuit traced and attracrs the armatures '1' and Ir" thereby breaking the circuit through the operators wires 1.) and 90 so that any contacts which may be made by the wipers connected with the conductors 19 and 20, will have no effect upon the pparatus of the trunk. \Vhen the switch S moves out of its int'ial position, the contacts It and 6 separate but the battery connection is maintained so long as the wiper s is passing over busy contacts 5 as, where those contacts are busy, the armature 2r will be attracted and circuit to the battery from each of those contacts will he made by the armature just referred to. When, however. an idle contact is reached. the circuit of the relay R is broken and is subsequently maintained opened by the cncrgization of the relay It, when the circa lzrreiay it armature thereby breaking the cir' broken at the armature 11'. The connection between the calling and called subscribers stations having been established, the called subscriber having been rung and having answered by removing his receiver, from its hook, conversation can be carried on between the two subscribers, the operators set having been automatically cut out upon the establishment of the connection as before set forth. At the termination of the conversation, the apparatus will be restored to its normal position b the hanging up of receivers' The hanging up of the calling subscribers receiver breaks the circuit at the hook through his instrument thereby breaking the circuit of the relays R and R where upon their armatures are released and the circuit of the cut out relay N is broken. The arniatures of this relay being released, the line wires 1 and 2 of the calling subscriber are disconnected from their extensions 4 and 5. The armature n being released, connects one of the contacts a, b with ground through the conductor 12 and the switch S being out of its initial position, the contacts a and b are in contact. The circuit of the release magnet can then be traced from the battery wire 3 through the conductor 6, armature m, conductor 10, magnet a, contacts a and I), conductor 12 and armature n to ground. The release magnet will thus be energized and the holding pawl will be removed from engagement with the ratchet upon the switch shaft whereupon the switch will return to its initial position. The magnet R being deenergized, its annat'ure 31 will break the circuit of the magnet R.

The armature 7-, however, is arranged to act slugglishly when released so that the connection of the conductor with the battery wire is maintained after the arma Lures 27' and 32" have come against their back contacts. This being the case, it will be seen that the two sides 15 and 16 of the trunk are simultanemisly connected with battery, this results in the simultaneous energization ot the relays V and V, the circuit of the relay V being traceable from the trunk conductors 41 through the relay V and comluctor 65 to ground while the circuit of the relay V is traceable from the trunk conductor 42 through relay V to ground. Relays V and V having been thus energized and their armatures attracted, circuit may be traced from battery wire 52, release relay Q, conductor 58, conductor 64, bank contact 8, wiper 5 release Q, conductor 33, side switch arm 8 and conductor 39 to ground. The release relays f and Q. being thus energized will attract thcir armaturcs when the circuits of the release mgnet 1 and r," of the switches S and re spectivcly will he closed whereupon those swit hes will he released and will rcmrn to their normal positions circuits when calling.

I do not herein claim broadly the system of tri-hcaded trunks or secondary distributing means for operators trunks, inasmuch as said subjects matter are claimed in my copending applications Serial Nos. 369201., filed April 20, 1907; 383,874, filed July 15, 1907, and 383,875, filed July 15, 1907.

\\"hat I claim is:

1. In a telephone exchange system, the combination with line circuits and subscribers instruments of a plurality of connecting links, automatic switches individual to the lines tor connecting. said line circuits and links, automatic means for moving any of said switches into position to connect a subscribers line with an idle link, said automatic means being set into operation by the single act of removing a subscribers receiver, an operators position, and automatic means individual to the connecting links set into operation by the same primary act to connect the subscriber thereto, together with directively driven switches con trolled by the operators to connect the links with wanted lines, substantially as described.

2. In a telephone exchange system, the combination with line circuits and subscribcrs instruments of a plurality of connecting links, automatic switches individual to the subscribers lines and each having a bias to its initial position, for connecting said line to the links. means for moving said switches set into operation by the single act of removing a subscrilwfs receiver, automatic selective switches adapted to connect the links and thereby the calling lines to the lines wanted. an operators set, and further automatic means individual to the links for connecting the same to a line when calling, substantially as described.

3. In a telephone exchange system, a plurality of line. circuits, a plurality of connect-- ing links, automatic switches for connecting the same to calling lines, other automatic switches for connecting the same to wante lines, means or actuating said automatic switches, an operators set, and automatic means individual to the links for connecting the said operator's set to a calling line, substantially as described.

4. In a telephone exchange system. a plu ralit of line circuits, a plurality of connecting inks, automatic switches for connecting the same to wanted lines, means for actuating said automatic switches comprising circuit closers and a power driven impulse generator controlled thereby, an operators set,

l cults, automatic step by'step and automatic switching means individuall to the links for connecting the said operators set to a calling line and link, substantially as described.

5. In a telephone exchange system, a plurality of subscribers lines, a plurality of automatic step by step connective circuits, switches individual to the lines for connecl l l l in said lines to said connective circuits, an operators controlling apparatus for sai connective circuits, and auxiliary step by step switching apparatus individual to the connective circuits for connecting the operators apparatus to the connective circuits in initiating a connection, substantially as described.

6. In a telephone exchange system, a plurality of line'circuits and a plurality of trunk lines less in number than the line cirswitches individual to the lines for connecting calling lines to said trunks, and other automatic switches for connecting the trunks to wanted lines, together with operators controlling apparatus for the trunks, and automatic step by step switches individual to the trunks for connecting the operators apparatus thereto. substantially as described.

7 In a telephone exchange system, a plurality of subscribers lines, a plurality of connective trunks, a plurality of line switches, one for each of said lines and operating step by step, each adapted to connect its line when calling to an idle trunk, an automatic selector switch constituting the calling terminal of each trunk, an operators impulse transmitting 211))?11'3tl15 for actuating said selector switch, ant auxiliary selector switches, one for each trunk, operating step by step, to automatically connect the operators apparatus when idle to a trunk when calling, substantially as described.

8. in a telephone exchange system, a plurality oi line circuits, a plurality of con ncctive trunks therefor less in number than the number of lines, a primary step b step seleitor switch for each line circuit a apted to connect a trunk with the calling line, a selector switch constituting the coi'inecting or calling terminal of the trunk, operators switch controlling apparatus, and a secondary step by step selector switch per trunk for connecting an operators controlling apparatus to the trunk, substantially as described.

9. In a telephone exchange system, a plurality of line circuits, a number of trunks less than the number of lines, automatic step by step switches for connecting calling lines with the trunks, automatic switches for conne ting the trunks with wanted lines, operators impulse transmitting apparatus and telephone sets. secondary step by step selector switches individual to the trunks for connecting the operators equipments with the trunks. and means for controlling the operation of the impulse transmitting apparatus when so connected. i

10. In a telephone exchange system, a plurality of line circuits, an operators controller and telephone set, a plurality of connecting trunks, automatic step by step switches for connecting the same to calling brought into lines, other automatic switches for connectl i ug the same to wanted lines, and still other automatic switches individual to the trunks for connecting the same to the operators set, with means for actuatingsaid automatic I switches, and for automatically restoring each one to its normal or zero position when l its service is finished, substantially as described. l

11. In a telephone exchange system, a switching center, a plurality of circuits entering said center, automatic apparatus individual to the entering circuits and connecting links associated therewith, normally disconnected from the entering circuits, means for moving said automatic apparatus l to connect the links with said circuits in response to calls thereover, further automatic apparatus for connecting the links with any desired circuits an operators telephone set and automatic means individual to the links for connecting the operators set with any of the links, substantially as described.

12. In a telephone exchange system, a switching center, a plurality of circuits contiguity at said center, switching apparatus individual to said eiri cuits and connecting links in said center normally disconnected from any of the entering circuits, means responsive to changes in any one of said circuits adapted to actuate the switching apparatus, so to connect the said circuit with an idle link, an operators set and automatic switching apparatus also responsive to said circuit changes, and individual to the links to connect the operators set wiih the same circuit, substantially as described.

13. In a telephone exchange system, a plu rality of line circuits converging to a central I otlice or switching center, a iiliu'ality of link circuits with automatic switching apparatus I individual to the lines but normally disconl nected from the line terminals, an operators l with automatic switchin apparatus as I sociatcd with the lines and links, and individual to the links but normally disconnected therefrom,

the operators set and also to an idle link, together with connective switches controlled from the operators set and arranged to connect the link circuits with wanted lines, sub stantially as described.

14. In a telephone exchange system, a plurality of line circuits converging to a switching center, a plurality of connective links and switching apparatus for each line at said center, an operators telephone set, and means acting autonniticully in response to a call over any line circuit, for actuating said switch apparatus to connect the line with an idle link and other automatic switching apparatus individual to the link to connect the link with an operators set, together with connective switches directively controlled by the operator and arranged to connect the links with wanted lines, substantially as described.

15. In a telephone exchange system, a plurality of line circuits entering a switching center, connective links and switching apparatus for each line at said center, operators telephones with means to associate them with any of the lines and links, and means acting automatically in response to a call over any line to actuate said switching apparatus so as to connect the line With an idle link and other automatic switching it paratus individual to the link to connect said link with an. idle operator s set, together with connective switches directively controlled by the operators to connect the links with wanted lines, substantially as described.

In testimony whereof I affix my signatu e in presence of two witnesses.

EDWVARD F]. CLFI'ME N T. lVitnesses i. STANLEY,

I E. time ,vs'ron, Jr

his line thereby to 

